Protective system



Dec. 16, 1930. s. L. BAUM 1,7

PROTECTIVE SYSTEM Filed July 16, 1928 Fig. 5.

Inventor: Se mouh L. Baum.

His Attor nqgf Patented Dec. 16, 1930 UNITED STATES PATENT OFFICEsnvmoun LEOIPOLD BAUM, or NEW ROCHELLE, NEW YORK, nssrenon 'ro GENERALELECTRIC COMPANY, A conronarron or NEW YORK PROTECTIVE sYs'rnmApplication filed July 16,

My invention relates to protective systems and particularly to systemsfor controlling the connections between two alternating current circuitsso that they are disconnected from each other in response topredetermined abnormal conditions of power flow between said circuitsand are connected togetherin response to a predetermined phase relationbetween the Voltages of the two circuits.

In certain types of electric circuits directional relay protection isdesirable. By 011- rectional protection is meant such operation that therelay will operate upon reversal of the direction of power flow. Suchprotection, for example, would be desirable at the end of a feeder,connecting a generating station with a substation. In this case, as longas power flows toward the substation conditions are normal, but shouldpower flow back from the substation the conditions would be abnormal andthe relay should begin to function. Another place where such a relay isdesirable is on a network switch which connects a bank of transformersto a secondary distribution grid in the streets. In this case the relayshould operate and open the network switch, were power to flow from thelow voltage mains in the street back into the transformers. In the caseof such a relay, however, an additional function is concerned, namely,that of reclosing the network switch when conditions again becomenormal.

In all the above described cases it has been assumed that the relay isto operate upon mere reversal of power regardless of the amount of powerinvolved. Usually, however, it is desirable to have the relay operateonly when the reverse power exceeds a certain amount, so calledreverse-power-overload protection.

This protectioncan not be given by an ordinary wattmeter type of reversepower relay for the following reason: When trounamed, the relay mightfail to function prop- 1928. Serial No. 293,189.

ble develops on an electric system, it is often accompanied by anextreme drop in voltage or potential. But as'before stated, in relays ofthe wattmeter type, the torque on the disc is proportional to theproduct of voltage and current, whence it follows that a reduction inthe voltage will materially decrease the operating torque on the disc ofthe relay, even though the current be very large due to a short circuitor other abnormal condition. In other words, when the relay isintendedto operate there is grave danger that the actuating torque will be verysmall and therefore any opposing or restraining torque on the disc, suchfor instance as a spring, must be very light. Were. a heavy spring orother large mechanical torque to be used to restrain the disc, to securethe overload-response feature aboveerly under a short circuit with theusual accompanying drop in voltage. In practice, therefore, reversepower protection has hitherto been obtained with a wattmeter type relay,but the overload protection with an entirel difierent type of apparatus,the operating contacts of each of the two relays being then connected inseries.

Furthermore a network relay, in addition to efiecting the opening of anetwork switch, also has to efiect the reclosing of the switch inresponse to the phase relation between the network voltage and thesecondary voltage of the network transformer.

On object of my invention is to provide an improved arrangement ofconnections for such a control rela whereby it effects the opening ofthe switc i in response to minimum values of reverse power which varydirectly with the voltage and efi'e'cts the closing of the switch when adesired phase relation exists between the voltages of the two circuitsand whereby the trippin characteristic'of the relay does not inter arewith the reclosing' characteristic of the relay.

My invention will be better understood from the following description,when taken in connection with the accompanying drawing and its scopewill be pointed out in the appended claims.

Referring to the accompanying drawing Fig. 1 illustratesdiagrammatically an arrangement of connections for a control relayembodying my invention, Fig. 2 is another arrangement of connectionsembodying my invention, and Figs. 3, land 5 illustrate othermodifications of my invention.

Referring to Fig. 1, 1 and 2 represent two electric circuits which arearranged to be connected together by suitable switching means 3. Theswitching means 3 may be provided with any suitable closing and trippingmeans, examples of which are so well known in the art that it is deemedunnecessary to illustrate them in the drawing. For controlling thetripping means of switching means 3 so that it is opened inresponse to aflow of power between the circuits 1 and 2 in a predetermined direction,I provide a reverse power relay 4 of the induction wattmeter type whichincludes a voltage winding 5 connected across the circuit 1 and twocurrent windings 6 and 7 which are respectivel energized in response tothe currents owing through the two main contacts of the switchin g means3 when closed. As shown the windings 6 and 7 are energized by thecurrent transformers 8 and 9 respectively. The windings 5, 6 and 7 areso arranged on the magnetic structure of the relay that they exert atorque proportional to El cos 9, where E is the voltage, I the currentand 6 the angle between E and I.

In order that the relay 4 may control the reclosin of the switchingmeans 3 in response to the phase relation between the voltages of thecircuits 1 and 2 when the switching means 3 is open, the relay is alsoprovided with the phasing windings 10 and 11 which are respectivelyconnected across the main terminals of the switching means 3 so that thewindings are energized in response to the instantaneous voltagedifierence between the two circuits 1 and 2. A suitable resistor such asa tungsten lamp 12 is connected in series with the phasing winding 10and a similar resistor or lam 13 is connected in series with the phasingwinding 11. The coils 5, 10 and 11 are so arranged on the magneticstructure of the relay 4 that the rela o erates in response to apredetermined p ase relation between the two voltages to effect thereelosing of the switching means 3.

Relays connected and arranged in the manner heretofore described havebeen used to control the operation of a network switch where it isdesired to effect the opening of the switch in response to a relativelysmall power reversal; Such relay arrangements, however, cannot be usedsatisfactorily in places where it is desired to arrange the relay sothat it has a relatively high reverse power setting because theoperation of the relay is materially affected by changes in the voltageof the circuit. For example, under low voltage conditions, which are aptto occur under short-circuit conditions, the abnormal reverse currentwhich is produced by the shortcircuit may not develop suflicient torquein the relay, due to the-low voltage, to cause the relay 'to operate inopposition to its normal biasing means to eiiect .the opening of theswitching means 3.

In accordance with my invention I provide an arrangement whereby therelay 4 at normal voltage has a relatively high reverse power settingand whereby the amount of reverse power required to operate the relaydecreases as the voltage of the interconnected circuits decreases. Iaccomplish this result by providing in opposition to the torque producedby the reverse power, a restraining torque which is proportional to thevoltage of the interconnected circuits. Therefore, the lower thevoltage, the smaller the torque produced by the reverse power has to bein order to operate the relay 4.

In the arrangement disclosed in Fig. 1, I obtain this restrainingtorque, which is proportional to the voltage of the circuits, byconnecting the phasing coils 10 and 11, an adjustable impedance I l andthe auxiliary contacts 15 on the switching means 3 in series across thecircuit 2 when the switching means 3 is closed. Therefore, when theswitching means 3 is closed and power is in the reverse direction thetorque T on the movable element of therelay is T=KEI cos 6KaE where E isthe voltage of the interconnected circuits, I is the current flowingbetween the circuits, 9 is the phase angle between E and I, K is aconstant, and K is a constant dependent upon the phase angle between thecurrents in windings 5 and 10, 11.

By providing the adjustable impedance 1% in the circuit of the windings10 and 11, it is possible to vary the phase angle between the current inthe windings 10 and 11 and the current in the winding 5 so as to varythe value of K and, therefore, the reverse power setting of the relay. 1

The auxiliary contacts 15 on the switching means 3 are provided in thecircuit of the windings 10 and 11 across the circuit 2 so that thiscircuit is opened when the switching means 8 is opened. Therefore. thevoltage restraint produced by the windings 10 and 11 during the trippingoperation of the relay has -no eiiect upon the reclosing characteristicof the relay.

In the modification shown in Fig. 2 I have shown my invention applied toanother well known type of network relay in which the two lCU currentwindings 6 and 7 are not* only respectively connected across thesecondary windings of the transformers 8 and 9 but are also respectivelyconnected in series with the resistance lamps 12 and 13 across the maincontacts of the switching means 3. In this modification the voltagerestraint is produced by the windings 10 and 11 which, in series withthe variable impedence 14 and the auxiliary contacts 15 on the switchingmeans 3, are connected across the circuit 1.

With the particular relay connections shown in Fig. 2 the windings 6 and7 function as the phasing windings and the windings 10 and 11 aredeenergized when the switching means 3 is open.

In Figs. 3 and 4 I have shown other modifications of my invention inwhich a voltage restraint is obtained by energizing the current windingof the relay in response to the voltage of the circuit in addition tothe current of the circuit. In order to simplify the disclosure thephasing connections of the relays have been omitted in these twofigures.

In Fig. 3 the current winding 6, in addition.

to being connected across the secondary of the current transformer 8 isalso connected in a series circuit with the variable impedance 14 andthe auxiliary contacts 15 across the circuit 1 when the switching means3 is closed.

In the modification shown in Fig. 4 both the voltage winding 5 and thecurrent winding 6 are energized from the secondary of a potentialtransformer 20, the primary of which is connected across the circuit 1.In series with the winding 6 is connected the variable impedance 14:.The winding 6 is also connected across the secondary of the currenttransformer 8.

It will be observed that the same reverse power characteristics areobtained with the combined current-restraint winding shown in Figs. 3and 4 as are obtained when the current windings and restraining windingsare separate windings as shown in Figs. 1 and 2.

All of the preceding description applies specifically to a single phasetype of relay. Similar constructions may, however, be used for polyphaserelays, each phase being considered and. treated independently andhaving its own potential winding and restraining winding. Another andperhaps better method of utilizing the windings which are in thepolyphase relay is to arrange the windings so that the potential windingof each phase will act with a restraining winding which is energizedfrom another phase. Such an arrangement is shown in Fig. 5 whichdiagrammatically illustrates a polyphase relay 4 which has the voltageand current windings of each element associated with one phase in themanner shown in Fig. 2, and the restraining winding connected across adifierent phase. For example, the voltage winding 5 and current winding6 of the upper element are energized respectively in response to thevoltage and current of the phase X of the circuit 1 whereas therestraining coil 10 of the upper element, in series with auxiliarycontacts 15 and a variable impedance 14, is connected across phase Zwhen the switch 3 is closed. In a similar manner the voltage winding 5and current winding 6 of the middle element are energizedrespectively inresponse to the voltage and current of phase Y of the circuit and therestraining winding 10 of the middle element is connected across phase Xwhenthe switch 3 is closed, and the voltage winding5 and current winding6 of the lower element are energized respectively in response to thevoltage and current of phase Z of the circuit and the restrainingwinding 10 of the lower element is connected across phase Y when theswitch 3 is closed. The advantage of this method over the first is thefollowing: In the first method if the voltage on any one phase, such forexample as on phase X only, drops to zero due to a short circuit, thenthe restraining torque is reduced to two-thirds of its normal value. Inthe second method, however, the two restraining coils are aflt'ected andthe torque is reduced to one-third of its normal value, thereby makingthe relay correspondingly more sensitive.

Referringonce more to the above equation T KEI cos 9 KaE it will beobserved that, with a constant current, the operating torque on the discwill increase with a decrease in voltage within certain limits. In otherwords, in the case of a short circuit, with a severe voltage drop, thenearer the fault, the faster the relay will operate. This gives therelay impedance characteristics and if these relays are placed atdifferent points along the feeder, the one nearest the trouble willalways be the first to respond.

My device thus has the following advantages and points of novelty:

1. The relay combines overload current and directional current responsein a single disc type. which operates as rapidly or even more rapidly atreduced potential than at full voltage.

2. The fact that the restraining coilis energized only while themain'switch is closed allows the characteristics mentioned above to becombined with normal characteristics of a network relay for closingconditions.

3. I have provided arelay wherein the speed of action is proportionaldirectly to the current and inversely to the voltage, and having asingle disc and a single set of contacts,

that is, a relay operating in response to the impedance drop or ahmicdrop without requiring any additional apparatus, such as coils, plungersand the like.

4. The possibilityof giving an ordinary wattmeter type induction relayany of the above described characteristics by connecting the currentcoil so that it is energized in accordance with both the current and thevolta e of the circuit, as shown for example in Figs. 3 and 4.

5. Any of the above characteristics may be embodied in a polyphase relayas well as in a single phase type.

While I have, in accordance with the patent statutes, shown anddescribed several em-.

bodiments of my invention, other changes and modifications will beobvious tothose skilled in the art, and I, therefore, aim in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of my invention.

I claim:

1. In combination, two electric circuits, a switch connecting saidcircuits, and a control relay responsive to a minimum reverse powervalue which varies with the volta e of the interconnected circuits whensaid switch is closed and responsive to the phase relation between thevoltages of said circuits when said switch is open including meanscontrolled by said switch for producing a restraining torque in saidrelay which circuits when said switch-is open including said circuitswhen said switch 18 open includtwo windings arranged to produce arestraining torque which varies with the voltage of said circuits, andcontacts in the circuit of one of said windings controlled by saidswitch so that said windings produce said restraining torque only whensaid switch is closed.

3. In combination, two electric circuits, a switch connecting saidcircuits, and a combined power directional and phasing relayresponsiveto power flow between said circuits in a predetermined direction whensaid 1 switch is closed and responsive to a predetermined phase relationbetween the voltages of ing a voltage winding, a current winding, arestraining winding, a circuit for said restraining winding across oneof said electric circuits, and contacts in the circuit of saidrestraining winding controlled by said switch.

4. In combination, two electric circuits, a switch connecting saidcircuits, and a combined power directional and phasing relay responsiveto power flow between said circuits in a predetermined direction whensaid switch is closed and responsive to a predetermined phase relationbetween the voltages of said circuits when said switch is open includinga voltage winding responsive to the voltage of one of said circuits, acurrent winding responsive to the current flowing through said switch, aphase winding responsive to the voltage diii'erence between saidcircuits when said switch is open, and means responsive to the closingof said switch for connecting said phasing winding across one of saidcircuits whereby said phasing winding coperates with said voltagewinding to produce a restraining torque which carries directly with thevoltage of said one of said circuita,

5. In combination, two polyphase circuits, :1 switch connecting saidcircuits, and a polyphase relay responsive to a minimum reverse powervalue which varies with the voltage of one of said circuits when saidswitch is closed and responsive to the phase relation between thevoltages of the corresponding phases of said circuits when said switchis open including an operating element associated with each phase andhaving a voltage winding responsive to the voltage of the associatedphase, a current winding responsive to the current in the associatedphase, and a restraining winding responsive to the voltage of anotherphase.

6. In combination, a polyphase circuit, and a polyphase relay responsiveto a minimum reverse 'power value which varies with the voltage of thesaid circuit including coopcrating voltage windings respectivelyenergized from different phases of said circuit for producing arestraining torque in opposition to the torque produced by a reversal ofpower.

7. In combination, a polyphase circuit, and a polyphase relay responsiveto a minimum reverse power value which varies with the voltage of saidcircuit including a plurality of reverse power elementsrespectivelyassociated with difi'erent phases of said circuit, each elementincluding a voltage winding responsive to the voltage of the associatedphase, a current winding responsive to the current in the associatedphase and a re stfi-aining winding energized from another p ase.

8. In combination, a polyphase circuit and a poly phase reverse powerrelay connected in said'circuit and including avplura'lity' of torqueproducing means respectively energized in response to the power indifferent phases of said circuit, each of said torque producing meansincluding two voltage windings respectively responsive to the voltagesof difierent phases of said circuit whereby difi'erent values of reversepower are required 'to effect the operation of said rela'y when thevoltage of said circuit varies.

9. In combination, two polyphase circuits, a switch connecting saidcircuits and a polyphase relay responsive to the power flow between saidcircuits when said switch is closed and to a predetermined phaserelation between'corresponding phase voltages of said Patent No.1,785,718.

hereto. I

SEYMOUR L. BAUM.

CERTIFICATE OF CORRECTION.

Granted December 16, 1930, to

SEYMOUR LEOPOLD BAUM.

It is hereby certified that error appears in-the printed specificationof the above numbered patent requiring correction as follows: Page 1,line 80, for the word "On" read'One; page 3, line [25, claim 3, for"ahmic" read ohmic; page 4, line 68, claim 4, for the word "phase" readphasing, and line 75, same claim, for the word"'carries" read varies;and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office. v

Signed and sealed this 13th day of January, A. D. 1931.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

